Ultrasound Handpiece

ABSTRACT

A handpiece having at least one set of piezoelectric elements polarized to produce longitudinal motion when excited at the relevant resonant frequency. The piezoelectric crystals are connected to an ultrasonic horn to which a cutting tip is attached. The horn and/or the cutting tip contains a plurality of diagonal slits or grooves. The slits or grooves produce optimized torsional movement in the cutting tip when the piezoelectric crystals are excited at a second resonant frequency.

This application is a continuation of U.S. patent application Ser. No.11/183,591, filed Jul. 18, 2005, which is a continuation-in-partapplication of U.S. patent application Ser. No. 10/916,675, filed Aug.12, 2004.

BACKGROUND OF THE INVENTION

This invention relates to ultrasonic devices and more particularly todevices for tuning and controlling an ophthalmic phacoemulsificationhandpiece.

A typical ultrasonic surgical device suitable for ophthalmic proceduresconsists of an ultrasonically driven handpiece, an attached hollowcutting tip, an irrigating sleeve and an electronic control console. Thehandpiece assembly is attached to the control console by an electriccable and flexible tubings. Through the electric cable, the consolevaries the power level transmitted by the handpiece to the attachedcutting tip and the flexible tubings supply irrigation fluid to and drawaspiration fluid from the eye through the handpiece assembly.

The operative part of the handpiece is a centrally located, hollowresonating bar or horn directly attached to a set of piezoelectriccrystals. The crystals supply the required ultrasonic vibration neededto drive both the horn and the attached cutting tip duringphacoemulsification and are controlled by the console. The crystal/hornassembly is suspended within the hollow body or shell of the handpieceat its nodal points by relatively inflexible mountings. The handpiecebody terminates in a reduced diameter portion or nosecone at the body'sdistal end. The nosecone is externally threaded to accept the irrigationsleeve. Likewise, the horn bore is internally threaded at its distal endto receive the external threads of the cutting tip. The irrigationsleeve also has an internally threaded bore that is screwed onto theexternal threads of the nosecone. The cutting tip is adjusted so thatthe tip projects only a predetermined amount past the open end of theirrigating sleeve. Ultrasonic handpieces and cutting tips are more fullydescribed in U.S. Pat. Nos. 3,589,363; 4,223,676; 4,246,902; 4,493,694;4,515,583; 4,589,415; 4,609,368; 4,869,715; and 4,922,902, the entirecontents of which are incorporated herein by reference.

When used to perform phacoemulsification, the ends of the cutting tipand irrigating sleeve are inserted into a small incision ofpredetermined width in the cornea, sclera, or other location in the eyetissue in order to gain access to the anterior chamber of the eye. Thecutting tip is ultrasonically vibrated along its longitudinal axiswithin the irrigating sleeve by the crystal-driven ultrasonic horn,thereby emulsifying upon contact the selected tissue in situ. The hollowbore of the cutting tip communicates with the bore in the horn that inturn communicates with the aspiration line from the handpiece to theconsole. A reduced pressure or vacuum source in the console draws oraspirates the emulsified tissue from the eye through the open end of thecutting tip, the bore of the cutting tip, the horn bore, and theaspiration line and into a collection device. The aspiration ofemulsified tissue is aided by a saline flushing solution or irrigantthat is injected into the surgical site through the small annular gapbetween the inside surface of the irrigating sleeve and the outsidesurface of the cutting tip.

There have been prior attempts to combine ultrasonic longitudinal motionof the cutting tip with rotational motion of the tip, see U.S. Pat. No.5,222,959 (Anis), U.S. Pat. No. 5,722,945 (Anis, et al.) and U.S. Pat.No. 4,504,264 (Kelman), the entire contents of which are incorporatedherein by reference. These prior attempts have used electric motors toprovide the rotation of the tip which require O-ring or other seals thatcan fail in addition to the added complexity and possible failure of themotors.

There have also been prior attempts to generate both longitudinal andtorsional motion without the use of electric motors. For example, inU.S. Pat. Nos. 6,028,387, 6,077,285 and 6,402,769 (Boukhny), one of theinventors of the current invention, describes a handpiece having twopairs of piezoelectric crystals are used. One pair is polarized toproduct longitudinal motion. The other pair is polarized to producetorsional motion. Two separate drive signals are used to drive the twopairs of crystals. In actual practice, making a handpiece using twopairs of crystals resonate in both longitudinal and torsional directionsis difficult to achieve. One possible solution, also described by one ofthe current inventors, is described in U.S. Patent Publication No. US2001/0011176 A1 (Boukhny). This reference discloses a handpiece have asingle set of piezoelectric crystals that produces longitudinal motion,and a series of diagonal slits on the handpiece horn or tip that producetorsional motion when the horn or tip is driven at the resonatefrequency of the piezoelectric crystals. Again, in practice, theresonate frequency of the piezoelectric crystals and the tip or horn didnot coincide, so simultaneous longitudinal and torsional motion wasdifficult to achieve.

Accordingly, a need continues to exist for a reliable ultrasonichandpiece that will vibrate both longitudinally and torsionally, eithersimultaneously or separately.

BRIEF SUMMARY OF THE INVENTION

The present invention improves upon prior art ultrasonic handpieces byproviding a handpiece having at least one set of piezoelectric elementspolarized to produce longitudinal motion when excited at the relevantresonant frequency. The piezoelectric crystals are connected to anultrasonic horn to which a cutting tip is attached. The horn and/or thecutting tip contains a plurality of diagonal slits or grooves. The slitsor grooves produce optimized torsional movement in the cutting tip whenthe piezoelectric crystals are excited at a second resonant frequency.

It is accordingly an object of the present invention to provide anultrasound handpiece having both longitudinal and torsional motion.

It is a further object of the present invention to provide an ultrasoundhandpiece with a horn having a series of diagonal slits to producetorsional motion.

Other objects, features and advantages of the present invention willbecome apparent with reference to the drawings, and the followingdescription of the drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the handpiece of the present inventionwith the outer case removed.

FIG. 2 is a perspective view of the ultrasonic horn that may be usedwith the handpiece of the present invention.

FIG. 3 a block diagram of a driving circuit that may be used with thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

As best seen in FIG. 1 handpiece 10 of the present invention generallycomprises ultrasonic horn 12, typically made from a titanium alloy. Horn12 has a plurality of helical slits, which will be discussed below. Aplurality (typically 1 or 2 pairs) of ring-shaped piezoelectric elements14 are held by compression nut 15 against horn 12. Aspiration shaft 16extends down the length of handpiece 10 through horn 12, piezoelectricelements 14, nut 15 and through plug 18 at the distal end of handpiece10. Aspiration tube 16 allows material to be aspirated through hollowtip 20, which is attached to horn 12, and through and out handpiece 10.Plug 18 seals outer shell 11 of handpiece 10 fluid tight, allowinghandpiece 10 to be autoclaved without adversely affecting piezoelectricelements 14. Additional grooves 22 for sealing O-ring gaskets (notshown) are provided on horn 12.

As best seen in FIG. 2, horn 12 contains a plurality of spiral slits 24.Preferably, the width of slits 24 is between 2% and 65% of the outsidediameter of horn 12. This, of course, will affect how many slits 24 canbe made on horn 12 (e.g., if slits 24 are 65% of the diameter of horn12, then only one slit 24 may be cut into horn 12). The width of slits24 selected will depend upon the desired amount of torsional movement.The depth of slits 24 in horn 12 preferably is between 4% and 45% of theoutside diameter of horn 12. Slits 24 may have a flat or square cutbottom, but preferably have a rounded or radiused bottom, which areeasier to manufacture. The length of slits 24 preferably is between 8%and 75% of the length of the larger diameter of horn 12. The pitch ofslits 24 preferably is between 125% and 500% of the larger diameter ofhorn 12. By way of example, the inventors have found that one suitableconfiguration of slits 24 on horn 12 with an outside diameter of 0.475inches is a total of eight slits 24, having a width of 0.04 inches, adepth of 0.140 (with a full radius bottom), a length of 0.7 inches and apitch of 1.35 inches gives suitable torsional movement of horn 12without compromising the longitudinal movement of horn 12.

As best seen in FIG. 1, the location of longitudinal and torsional nodalpoints (the points with zero velocity of the respective mode) isimportant for proper functioning of handpiece 10. The torsional node 26preferably is located at the proximal longitudinal node 28, so that thetorsional node 26 and the longitudinal node 28 are coincident, e.g.,both of which are located on plug 18. Handpiece 10 also contains adistal longitudinal node 30 located at reduced diameter portion 32 ofhorn 12.

As best seen in FIG. 3, drive circuit 34 that may be used with handpiece10 of the present invention preferably is similar to that described inU.S. Pat. No. 5,431,664, the entire contents of which being incorporatedherein by reference, in that drive circuit 34 tracks admittance ofhandpiece 10 and controls the frequency of handpiece 10 to maintain aconstant admittance. However, drive circuit 34 monitors both thetorsional mode and the longitudinal mode and controls these modes inhandpiece 10 using two different drive frequencies. Preferably, thetorsional drive signal is approximately 32 kHz and the longitudinaldrive signal is 44 kHz, but these frequencies will change depending uponthe piezoelectric elements 14 used and the size and shape of horn 12 andslits 24. Although both the longitudinal or the torsional drive signalmay be supplied in a continuous manner, preferably the longitudinaldrive signal and the torsion drive signal are alternated, so that thedrive signal is provided in a desired pulse at one frequency and thenswitched to the other frequency for a similar pulse, with no overlapbetween the two frequencies, but no gap or pause in the drive signal.Alternatively, the drive signal can be operated in a similar manner asdescribed, but short pauses or gaps in the drive signal can beintroduced. In addition, the amplitude of the drive signal can bemodulated and set independently for each frequency.

The pause or gap between drive signals can serve various purposes. Onepurpose is to allow for the ultrasound movement of piezoelectricelements 14 and horn 12 to attenuate or stop so that lens fragments canonce again be suctioned to tip 20 and an occlusion reestablished,thereby increasing the holding force on the lens fragment.Reestablishing the occlusion will increase cutting efficiency of thefollowing pulse of ultrasound, whether longitudinal or torsional.Another purpose of the pause or gap between drive signals is to allowfor the ultrasound movement of piezoelectric elements 14 and horn 12 toattenuate or stop prior to the other (either longitudinal or torsional)mode being excited. Such attenuation between drive signals will reduceamount of potential non-linear interactions in the system which cangenerate undesirable heat and lead to premature degradation ofpiezoelectric elements 14 or mechanical failure of the entire assembly.

Alternatively, there can be a slight overlap in the longitudinal andtorsional drive signals. The overlap may provide relatively short timeintervals when the added action of both torsional and longitudinaldisplacements results in especially fast rate of lens emulsification,and yet the overlap is short enough to prevent piezoelectric elements 14from premature degradation or failure of the entire mechanical assemblyas a result of excessive stress.

Yet another alternative if to have both longitudinal and torsional drivesignals overlap completely thus resulting in applying high stress levelsto the lens material when the two signals overlap, and yet leaving apause in between for the occlusion to reestablish itself and vacuumbuild-up, thus improving efficiency of the following pulse application.

Still another alternative is to apply a continuous longitudinal signalwith a pulsed torsional signal, or vice versa, a continuous torsionalsignal with a pulsed longitudinal signal. Continuous application oftorsional ultrasound does not cause repulsion because tip 20 movement isoriented perpendicular to the direction of the engagement of tip 20 withthe lens, and the pulsed applications of longitudinal ultrasound areshort enough to prevent overheat or mechanical damage to piezoelectricelements 14.

Finally, as discussed above, both the longitudinal and torsional drivesignals can be applied continuously and simultaneously, with theamplitudes of the both signals being selected such that overheating andexcessive mechanical stress on the system is reduced. If such a drivescheme is to be used, two sets of piezoelectric elements 14 arepreferred with the torsional signal being applied to one set, whilelongitudinal signal applied to the other set.

While certain embodiments of the present invention have been describedabove, these descriptions are given for purposes of illustration andexplanation. Variations, changes, modifications and departures from thesystems and methods disclosed above may be adopted without departurefrom the scope or spirit of the present invention.

1. An ultrasonic handpiece, comprising: a handpiece shell; an ultrasoundhorn held within the shell; and a plurality of piezoelectric elementsconnected to the horn, the piezoelectric elements producing torsionalmovement in the horn in response to a drive signal having a firstfrequency and a first amplitude and longitudinal movement in the horn inresponse to a drive signal having a second frequency and a secondamplitude; wherein the drive signal having the first frequency isalternated with the drive signal having the second frequency; andfurther wherein the piezoelectric elements and the horn are held withinthe shell so that a torsional nodal point and a proximal longitudinalnodal point are coincident at a plug; and further wherein the shell isless than 100 centimeters in length.
 2. The apparatus of claim 1 whereinthe drive signal having the first frequency and the drive signal havingthe second frequency do not overlap.
 3. The apparatus of claim 1 whereinthe drive signal having the first frequency and the drive signal havingthe second frequency overlap.
 4. An ultrasonic handpiece, comprising: ahandpiece shell; an ultrasound horn held within the shell; and aplurality of piezoelectric elements connected to the horn, thepiezoelectric elements producing torsional movement in the horn inresponse to a drive signal having a first frequency and a firstamplitude and longitudinal movement in the horn in response to a drivesignal having a second frequency and a second amplitude; wherein thedrive signal having the first frequency is applied continuously and thedrive signal having the second frequency is pulsed; and further whereinthe piezoelectric elements and the horn are held within the shell sothat a torsional nodal point and a proximal longitudinal nodal point arecoincident at a plug; and further wherein the shell is less than 100centimeters in length.
 5. An ultrasonic handpiece, comprising: ahandpiece shell; an ultrasound horn held within the shell; and aplurality of piezoelectric elements connected to the horn, thepiezoelectric elements producing torsional movement in the horn inresponse to a drive signal having a first frequency and a firstamplitude and longitudinal movement in the horn in response to a drivesignal having a second frequency and a second amplitude; wherein thedrive signal having the first frequency is pulsed and the drive signalhaving the second frequency is applied continuously; and further whereinthe piezoelectric elements and the horn are held within the shell sothat a torsional nodal point and a proximal longitudinal nodal point arecoincident at a plug; and further wherein the shell is less than 100centimeters in length.
 6. An ultrasonic handpiece, comprising: ahandpiece shell; an ultrasound horn held within the shell, the horncontaining a plurality of circumferential, diagonal slits sized andspaced so as to produce torsional movement in the horn in response to adrive signal having a first frequency and longitudinal movement in thehorn in response to a drive signal having a second frequency; and aplurality of piezoelectric elements; wherein the drive signal having thefirst frequency and the drive signal having the second frequency areapplied continuously; and further wherein the piezoelectric elements andthe horn are held within the shell so that a torsional nodal point and aproximal longitudinal nodal point are coincident at a plug; and furtherwherein the shell is less than 100 centimeters in length.
 7. Anultrasonic handpiece, comprising: a handpiece shell; an ultrasound hornheld within the shell; and a plurality of piezoelectric elementsconnected to the horn, the piezoelectric elements producing torsionalmovement in the horn in response to a drive signal having a firstfrequency and a first amplitude and longitudinal movement in the horn inresponse to a drive signal having a second frequency and a secondamplitude; wherein the drive signal having the first frequency and thedrive signal having the second frequency are provided in pulses thatoverlap completely; and further wherein the piezoelectric elements andthe horn are held within the shell so that a torsional nodal point and aproximal longitudinal nodal point are coincident at a plug; and furtherwherein the shell is less than 100 centimeters in length.
 8. Theultrasonic handpiece of claim 1 wherein the first amplitude and thesecond amplitude are modulated.
 9. The ultrasonic handpiece of claim 4wherein the first amplitude and the second amplitude are modulated. 10.The ultrasonic handpiece of claim 5 wherein the first amplitude and thesecond amplitude are modulated.
 11. The ultrasonic handpiece of claim 7wherein the first amplitude and the second amplitude are modulated. 12.An ultrasonic handpiece comprising: a handpiece shell; an ultrasonichorn at least partially located in the shell; a piezoelectric elementconnected to the horn, the piezoelectric element producing torsionalmovement in the horn in response to a drive signal having a firstfrequency and longitudinal movement in the horn in response to a drivesignal having a second frequency; and a plug for sealing the outershell; wherein a torsional nodal point and a longitudinal nodal pointare coincident at the plug; and further wherein the shell is less than100 centimeters in length.
 13. The handpiece of claim 12 wherein thedrive signal having the first frequency is alternated with the drivesignal having the second frequency.
 14. The handpiece of claim 12wherein the drive signal having the first frequency is appliedcontinuously and the drive signal having the second frequency is pulsed.15. The handpiece of claim 12 wherein the drive signal having the firstfrequency is pulsed and the drive signal having the second frequency isapplied continuously.
 16. The handpiece of claim 12 wherein the drivesignal having the first frequency and the drive signal having the secondfrequency are applied continuously.
 17. The handpiece of claim 12wherein the drive signal having the first frequency and the drive signalhaving the second frequency are provided in pulses that overlap.
 18. Anultrasonic handpiece comprising: a handpiece shell; an ultrasonic hornat least partially located in the shell and coupled to the shell at aplug location; and a piezoelectric element connected to the horn, thepiezoelectric element producing torsional movement in the horn inresponse to a drive signal having a first frequency and longitudinalmovement in the horn in response to a drive signal having a secondfrequency; wherein a torsional nodal point and a longitudinal nodalpoint are coincident at the plug location; and further wherein the shellis less than 100 centimeters in length.
 19. The handpiece of claim 18wherein the drive signal having the first frequency is alternated withthe drive signal having the second frequency.
 20. The handpiece of claim18 wherein the drive signal having the first frequency is appliedcontinuously and the drive signal having the second frequency is pulsed.21. The handpiece of claim 18 wherein the drive signal having the firstfrequency is pulsed and the drive signal having the second frequency isapplied continuously.
 22. The handpiece of claim 18 wherein the drivesignal having the first frequency and the drive signal having the secondfrequency are applied continuously.
 23. The handpiece of claim 18wherein the drive signal having the first frequency and the drive signalhaving the second frequency are provided in pulses that overlap.